The mechanism of action of a single dose of methylprednisolone on acute inflammation in vivo

Is there any potential management against COVID-19? A systematic review and meta-analysis

PURPOSE

A recent survey has shown that the COVID-19 pandemic has culminated in dramatical and critical treatment particularly in acute infected patients. In fact, this systematic review-meta-analysis was directly pertained to estimation at the efficient value of some clinical managements to confront the COVID-19 infection.

METHODS

Pubmed, Embase, Scopus, Cochrane, and Scholar databases were searched from inception to July 1, 2020, to identify studies reporting the current treatment process and medications (e.g. hydroxychloroquine, antiviral therapy, convalescent plasma, and immunomodulatory agents) for COVID-19. A random-effects model meta-analysis was performed to calculate the relative risk (RR) with 95% confidence intervals (CI). The outcomes of this study were the frequency of negative conversion cases, clinical improvements, mechanical ventilation demand, intensive care unit (ICU) entry, and mortality. The standard treatment refers to the published guidelines and specialist experience which varies in different articles, and the proposed treatment refers to the kind of interest suggested in the included studies.

RESULTS

A number of 45 articles met the eligibility criteria (out of 6793 articles). Among them, 26 articles involving 3263 patients were included in quantitative analysis. Anti-COVID-19 interventions could significantly increase clinical improvement (RR 1.17, 95% CI 1.08-1.27; I2 = 49.8%) and reduce the mortality rate (RR 0.58, 95% CI 0.35-0.95; I2 = 74.8%). Although in terms of negative conversion, ICU entry, and mechanical ventilation demand, clinical intervention had no beneficial effect. The clinical effect of immunomodulatory agents (especially tocilizumab and anakinra) was noticeable compared to other medications with RR of 0.22 (95% CI 0.09-0.53; I2 = 40.9%) for mortality and 1.25 (95% CI 1.07-1.46; I2 = 45.4%) for clinical improvement. Moreover, Antivirals (RR 1.13, 95% CI 1.01-1.26; I2 = 47.0%) and convalescent plasma therapy (RR 1.41, 95% CI 1.01-1.98; I2 = 66.6%) had significant beneficial effects on clinical improvement.

CONCLUSION

Based on our findings, all the included interventions significantly declined the mortality and enhanced clinical improvements with no effect on negative conversion and mechanical ventilation demand. Especially, immunomodulators and plasma therapy showed favorable outcomes. An evaluation on the efficacy of proposed treatment against COVID-19.

Immunosuppression for in vivo research: state-of-the-art protocols and experimental approaches

Almost every experimental treatment strategy using non-autologous cell, tissue or organ transplantation is tested in small and large animal models before clinical translation. Because these strategies require immunosuppression in most cases, immunosuppressive protocols are a key element in transplantation experiments. However, standard immunosuppressive protocols are often applied without detailed knowledge regarding their efficacy within the particular experimental setting and in the chosen model species. Optimization of such protocols is pertinent to the translation of experimental results to human patients and thus warrants further investigation. This review summarizes current knowledge regarding immunosuppressive drug classes as well as their dosages and application regimens with consideration of species-specific drug metabolization and side effects. It also summarizes contemporary knowledge of novel immunomodulatory strategies, such as the use of mesenchymal stem cells or antibodies. Thus, this review is intended to serve as a state-of-the-art compendium for researchers to refine applied experimental immunosuppression and immunomodulation strategies to enhance the predictive value of preclinical transplantation studies.

Tissue adhesiveness and host response ofin situ photopolymerizable interpenetrating networks containing methylprednisolone acetate

Interpenetrating networks (IPNs) of varying formulations were investigated as candidates for an in situ photopolymerizable drug delivery matrix containing poly(ethylene glycol) diacrylate and gelatin. The anti-inflammatory agent methylprednisolone acetate was loaded into the IPN. Bond strength between the IPN and tissue (i.e., muscle, dermis, skin) was determined by a modified American Society for Testing and Materials peel test at constant peel rate. The IPNs provided adhesion values of up to 5.7N, which were three- to fivefold lower than that of the commercial tissue bioadhesive. The subcutaneous cage implant system was utilized to assess material host response and drug efficacy in vivo. IPN formulations elicited a more intense acute inflammatory response than the empty cage controls. Methylprednisolone acetate loaded within the IPNs lowered the level of inflammatory response to levels that were comparable to the empty cage baseline controls. In conclusion, a methodology was developed to quantify the tissue adhesiveness of an in situ photopolymerized IPN matrix containing anti-inflammatory agents. The efficacy of drug-loaded IPN in affecting the host inflammatory response was demonstrated in vivo.

Thrombin inhibitor ameliorates secondary damage in rat brain injury: suppression of inflammatory cells and vimentin-positive astrocytes

The effects of the thrombin inhibitor argatroban on the number of inflammatory cells and reactive astrocytes were investigated in a rat brain injury model. Gelatin sponge soaked with thrombin inhibitor (treatment group) or saline (control group) was placed in the brain defect to assess the infiltration of inflammatory cells by hematoxylin-eosin and immunohistochemical staining. Expression of polymorphonuclear leukocytes (PMNs) and monocyte/macrophage (Mo/Mo) cells, and vimentin (VIM)-positive astrocytes and glial fibrillary acidic protein (GFAP)-positive astrocytes were compared between groups. In the treatment group, infiltration of both PMNs and Mo/Mo cells, and the number of VIM-positive astrocytes were significantly reduced, but the number of GFAP-positive astrocytes was not different from the control group. Thrombin inhibitor suppresses the infiltration of inflammatory cells and excessive gliosis caused by VIM-positive astrocytes, but not expression of GFAP-positive astrocytes, suggesting minimization of secondary brain damage and promotion of the conditions required for neural regeneration.

V antigen of Yersinia pestis inhibits neutrophil chemotaxis

V antigen (V), a secreted protein encoded by the 70 kb low-calcium response plasmid of Yersinia pestis, is an essential virulence factor. In animal models, it inhibits the early host inflammatory response to infection which is associated with decreased blood and tissue levels of proinflammatory cytokine synthesis. To elucidate further the pathogenetic mechanism(s) of V, in vitrosystems are needed to measure and analyse relevant functional activities of V. We studied the effect of V on the migration of neutrophils to a chemoattractant both in vivo and in vitro. Peripheral injection of V was associated with a reduction in the number of PMN migrating into s.c. sponges and i.p. exudates. Similarly, pre-incubating human peripheral blood neutrophils with >/=ng/ml V significantly inhibited the in vitro chemotactic response to the peptide chemoattractant FMLP. The inhibitory activity of V was inactivated by heat and was neutralized by rabbit polyclonal anti-V IgG as well as by sera from mice surviving infection with Y. pestis. Recombinant polyhistidine-tagged V fusion proteins retained biological activity compared to V proteins lacking the tag. Inhibition of chemotaxis appears to be the first demonstration of an in vitro biological effect of V and may be a useful model to elucidate its molecular mechanism of action.

Retinoic Acid Induces Aggregation of the Acute Promyelocytic Leukemia Cell Line NB-4 by Utilization of LFA-1 and ICAM-2

All-trans retinoic acid (tRA) is a potent differentiation agent that is effective therapy for acute promyelocytic leukemia (APL). However, 5% to 25% of patients develop retinoic acid syndrome, a potentially life-threatening complication in which the pathogenesis relates to adhesive alterations of APL cells. Therefore, we investigated the relationship between tRA-induced differentiation and the adhesive properties of APL cells. After confirming differentiation-related morphological changes of NB-4 cells in response to tRA, we showed that homotypic aggregation of NB-4 cells grown in tRA for 72 hours is dose-dependent with a median effective dose of approximately 50 nmol/L. Maximal aggregation occurred at mean and peak therapeutic serum concentrations (100 and 1,000 nmol/L, respectively). Aggregation also increased with the length of tRA exposure over 168 hours. Aggregation was inhibited by neutralizing antibodies against LFA-1 and ICAM-2. Notably, antibodies directed against VLA-4, other β2 integrins (Mac-1 and p150), or other potential LFA-1 counterstructures that were expressed on the cell surface (ICAM-1 and ICAM-3) did not block aggregation. Aggregation occurred with similar kinetics regardless of the presence of phorbol ester or the “activating” monoclonal antibody (MoAb) KIM 185, suggesting that the avidity of LFA-1 is not modulated on NB-4 cells in a manner similar to other leukocytes. Consistent with the prompt clinical effectiveness of methyl prednisolone sodium succinate (MPSS) in retinoic acid syndrome, MPSS rapidly inhibited homotypic aggregation in a dose-dependent manner. Thus, tRA alters the adhesive properties of APL cells by inducing the expression of high-avidity β2 integrins, aggregation is inhibited by LFA-1 and ICAM-2 MoAb, and tRA effects are rapidly reversible by MPSS. Taken together, our findings provide a clinically relevant system for study of LFA-1/ICAM-2 interaction and suggest a mechanism in part for retinoic acid syndrome and the effectiveness of MPSS in ameliorating retinoic acid syndrome.

Retinoic Acid Induces Aggregation of the Acute Promyelocytic Leukemia Cell Line NB-4 by Utilization of LFA-1 and ICAM-2

All-trans retinoic acid (tRA) is a potent differentiation agent that is effective therapy for acute promyelocytic leukemia (APL). However, 5% to 25% of patients develop retinoic acid syndrome, a potentially life-threatening complication in which the pathogenesis relates to adhesive alterations of APL cells. Therefore, we investigated the relationship between tRA-induced differentiation and the adhesive properties of APL cells. After confirming differentiation-related morphological changes of NB-4 cells in response to tRA, we showed that homotypic aggregation of NB-4 cells grown in tRA for 72 hours is dose-dependent with a median effective dose of approximately 50 nmol/L. Maximal aggregation occurred at mean and peak therapeutic serum concentrations (100 and 1,000 nmol/L, respectively). Aggregation also increased with the length of tRA exposure over 168 hours. Aggregation was inhibited by neutralizing antibodies against LFA-1 and ICAM-2. Notably, antibodies directed against VLA-4, other β2 integrins (Mac-1 and p150), or other potential LFA-1 counterstructures that were expressed on the cell surface (ICAM-1 and ICAM-3) did not block aggregation. Aggregation occurred with similar kinetics regardless of the presence of phorbol ester or the “activating” monoclonal antibody (MoAb) KIM 185, suggesting that the avidity of LFA-1 is not modulated on NB-4 cells in a manner similar to other leukocytes. Consistent with the prompt clinical effectiveness of methyl prednisolone sodium succinate (MPSS) in retinoic acid syndrome, MPSS rapidly inhibited homotypic aggregation in a dose-dependent manner. Thus, tRA alters the adhesive properties of APL cells by inducing the expression of high-avidity β2 integrins, aggregation is inhibited by LFA-1 and ICAM-2 MoAb, and tRA effects are rapidly reversible by MPSS. Taken together, our findings provide a clinically relevant system for study of LFA-1/ICAM-2 interaction and suggest a mechanism in part for retinoic acid syndrome and the effectiveness of MPSS in ameliorating retinoic acid syndrome.

Effect of methylprednisolone on small bowel, spleen and liver changes in a murine model of inflammatory bowel disease

The aim of this study was to evaluate the influence of methylprednisolone (1 mg/kg, i.p.) on inflammatory lesions in the small bowel, liver (pericholangitis) and spleen (lymphofollicular proliferation), in a model of inflammatory bowel disease induced by 2.4-dinitrofluorobenzene in previously sensitized BALB-c mice. As a parameter of corticosteroid anti-inflammatory and immunosuppressive action, we simultaneously investigated its effects on mononuclear cell accumulation within the ileal lamina propria and submucosa during the observed time period (1-30 days). We noted a significant decrease in accumulation of mononuclear cells within the lamina propria (P < 0.001). An effect on mononuclear cell infiltration within the ileal submucosa was also noted but was not statistically significant. In addition, pericholangitis in the liver and lymphofollicular proliferation in the spleen were not observed in the experimental group during treatment with methylprednisolone. The results of this study indicate that the previously described model of intestinal inflammation could be used in further research of present and new therapeutic modalities for inflammatory bowel disease.

Pulse methylprednisolone therapy in the treatment of Wegener's granulomatosis

Five patients with Wegener's granulomatosis were treated with high-dose intravenous methylprednisolone (MTP) pulse therapy. Three out of five patients received MTP pulse therapy as the initial treatment and remission was achieved. Renal biopsy after the treatment confirmed the improvement of kidney involvement in 2 cases. Although the other two patients received MTP pulse therapy when a relapse occurred, the therapy could not suppress the progression of the disease. These observations suggest that MTP pulse therapy when given early may make it possible to suppress the progression of kidney involvement and improve the prognosis of the disease. Furthermore, it may also decrease the total doses of oral steroids and cyclophosphamide because of a strong anti-inflammatory and immunosuppressive action and consequently diminish the side effects. In conclusion MTP pulse therapy as the initial treatment may be beneficial in treating patients with Wegener's granulomatosis.

Chemiluminescence of neutrophils in patients with glomerulonephritis treated with methylprednisolone

The effect of high dose methylprednisolone (Solu-Medrol, Up John) (1000 mg) on chemiluminescence (CL) of peripheral blood neutrophils in patients with various primary glomerulopathies was determined. Contrary to the well-established influence of corticosteroids on in vitro suppression of leukocytic chemiluminescence, our studies disclose a remarkable enhancement of neutrophil chemiluminescent activity in patients receiving pulse methylprednisolone infusion. Subsequent administrations of the drug did not result in any significant change of the analysed parameters. Increased chemiluminescence returned to the pretreatment values within approximately seven days. A possible explanation for the observed phenomenon is discussed.

The function of granulocytes and alveolar macrophages following a single dose of endotoxin in rabbits. Effects of methylprednisolone

It is a generally held opinion that steroids attenuate the activation of phagocytes. However, this statement has its limitations; in rabbit endotoxemia, for instance, steroids enhance the procoagulant activity of monocytes. The present study aimed to investigate the release of toxic oxygen metabolites (TOM) from granulocytes and alveolar macrophages 24 h after endotoxin injection in rabbits, and the effect of concomitant injection of methylprednisolone (MP). Release of TOM was assessed by peak chemiluminescence (CLP). Expression of thromboplastin activity by alveolar macrophages was determined as well, employing a recognized method for assessment of activity. In terms of mean +/- s.e.mean, endotoxin increased granulocyte count from a baseline value of 1.8 +/- 0.2 X 10(6) cells/ml to 3.7 +/- 1 X 10(6) cells/ml, which increased further to 9.8 +/- 2.5 X 10(6) cells/ml following administration of MP. Whereas endotoxin given alone caused no significant change in granulocyte CLP, additional administration of MP increased CLP from 1723 +/- 389 to 16610 +/- 8428 counts. On the other hand, MP attenuated an endotoxin-induced increase in both CLP and thromboplastin activity of alveolar macrophages. Thus, MP appears to have a proinflammatory effect on circulating granulocytes in rabbit endotoxemia, simultaneously depressing the function of stationary macrophages. This may suggest an injurious effect of MP in rabbit endotoxemia.

Collagen degradation by experimentally-induced subcutaneous granulation tissue in the rat

Granulation tissue provoked by implantation of cellulose sponge or a nylon bag degraded a powder of homologous collagen. This activity was located in a non-filtrable tissue fraction and was associated with the appearance of mononuclear and histiocytic giant cells, following an early polymorphonuclear-cell infiltration. The activity could be manipulated experimentally, indicating that this model can be used in investigations of inflammation-induced collagen degradation.

Steroid administration after myocardial infarction promotes early infarct expansion. A study in the rat

Whether steroids lead to thinner scars and larger aneurysms by delaying collagen deposition or worsening infarct expansion before significant collagen deposition begins is unknown. Rats underwent either transmural infarction by left coronary ligation or sham operation. Both infarct and sham rats were randomized to methylprednisolone 50 mg/kg i.p. X 4 or saline treatment within 24 h after operation. Sacrifice occurred before (3 d) or after (7 d) collagen deposition typically begins. Despite similar infarct size, infarct wall thickness was 1.35 +/- 0.08 mm in the saline and 0.99 +/- 0.12 mm in the methylprednisolone group (P less than 0.001) at 3 d. This decrease in wall thickness was explained by a decrease in the number of myocytes across the infarct wall (r = 0.99; P less than 0.001), suggesting that steroids promote myocyte slippage. Furthermore, methylprednisolone caused no further infarct thinning or cavity dilatation beyond 3 d. Thus, high-dose methylprednisolone given within 24 h after transmural infarction worsens infarct expansion before collagen is laid down by promoting the slippage of necrotic myocytes.

The cored sponge model of in vivo leucocyte chemotaxis

A method has been developed for the in vivo measurement of leucocyte chemotaxis in response to the bacterial chemotactic peptide F-met-leu-phe (FMLP). Polyurethane sponges were pre-treated with FMLP and implanted subcutaneously in rats and after a suitable interval removed for determination of leucocyte influx. In vivo concentration gradients of chemotactic factors within intact sponges were shallow and leucocyte accumulation unsatisfactory. Accordingly a cored sponge model was developed in which the cylindrical core only was treated with chemotactic factor and the sponge reassembled prior to subcutaneous implantation. Steep concentration gradients were established within the outer sponge matrix with marked effects on leucocyte accumulation, permitting studies of the time course of in vivo chemotaxis. With cored sponges test to control cell number ratios were maximal at 4 hours using both free and albumin-bound FMLP. This model of in vivo chemotaxis may prove useful in several areas of inflammation research.

Infarct size reduction: a review of the clinical trials

The most important finding to emerge from this review of experimental and clinical studies is that the earlier therapy is begun after the onset of symptoms of acute MI, the greater the potential for reduction of infarct size and possibly mortality. It is difficult to define a precise time after which therapy would not have an effect, since the clinical trials for each drug group vary significantly in respect to time of therapy initiation. In experimental studies, major salvage of ischemic myocardium occurs when the drug is given within two hours of coronary artery occlusion. If drug therapy is begun four to six hours postocclusion, then only minor or no reductions in infarct size will occur. The ability of any drug or intervention to reduce infarct size in humans would be optimized if therapy were begun less than four hours of onset of symptoms. With the realization of the wavefront phenomenon and the potential salvage of myocardium at risk with reperfusion, the introduction of reperfusion in the clinical setting with thrombolytic agents or other procedures becomes highly desirable. Clot-selective thrombolytic agents, such as tissue plasminogen activator, diminish the adverse effects and high costs of intracoronary thrombolytic therapy or PTCA. Consequently, it is probable that the initial procedure of choice would be the use of clot-selective thrombolytic therapy. Thrombolytic therapy only lyses thrombi and does not affect the underlying causes of the coronary artery occlusion. Therefore, therapy to reduce the chances of reinfarction and death must also be initiated. Percutaneous transluminal coronary angioplasty, in selected patients, should reduce the reocclusion rate. Beta-adrenoceptor blocking agents appear to be an excellent therapy for reducing mortality when administered chronically; these agents reduce myocardial oxygen consumption and reverse the imbalance between oxygen supply and oxygen demand caused by activation of the sympathetic nervous system and actions of catecholamines. Since thrombus formation has occurred at least once in patients who survive an MI, it is probable that the conditions for thrombus formation still exist. Therefore, institution of antiplatelet aggregating drugs, such as aspirin, would seem to be an appropriate prophylactic regimen. Beta blockers and possibly nitroglycerin have desirable effects when thrombolysis is unavailable. The efficacy of calcium-channel blocking agents on reduction of infarct size appears to be limited, although in the setting of stable and unstable angina postinfarction, these agents can play an important role.(ABSTRACT TRUNCATED AT 400 WORDS)

Relation of early mononuclear and polymorphonuclear cell infiltration to late scar thickness after experimentally induced myocardial infarction in the rat

This report describes the relationship between the intensity of early inflammation after acute myocardial infarction and the later thickness of the left ventricular (LV) scar. Histologic sections of hearts from methylprednisolone-treated (MP), cobra venom factor-treated (CVF), and untreated control rats that had been subjected to either 2 or 21 days of coronary artery occlusion were studied. In the rats examined at 2 days (n = 20 for MP, n = 16 for CVF, and n = 20 for controls), a semiquantitative inflammation score (1-4) was attributed to each infarct. Mononuclear (MN) cells were counted in 4 oil-immersion fields per section and polymorphonuclear (PMN) cells in 9 oil-immersion fields per section. In the rats examined at 21 days (n = 22 for MP, n = 22 for CVF, and n = 26 for controls), the thickness of the LV scar was measured every 1.6 mm along its circumference. Inflammation scores at 2 days were 3.5 +/- .6 for controls, 1.5 +/- .5 for MP, and 2.9 +/- .8 for CVF (p less than .05 among groups). The MN cells counted were 73 +/- 7 for controls, 47 +/- 5 for MP, and 61 +/- 9 for CVF (p less than .05 among groups). There was no difference in PMN infiltrate among groups. Scar thickness at 21 days were .9 +/- .1 mm for controls, .7 +/- .1 mm for MP, and .9 +/- .1 mm for CVF (MP compared to CVF and controls, p less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effects of glucocorticoid and indomethacin treatment on the acute inflammatory reaction in rabbits

We have recently shown that indomethacin and ASA diminish the elevated blood flow, protein exudation, and leukocyte infiltration during acute inflammation induced by killed Escherichia coli, the reversed Arthus reaction, or zymosan-activated plasma (ZAP; C5ades-arg) in rabbit skin. All of these effects were likely due to the inhibition by these drugs of prostaglandin (PG) synthesis in the lesions. Because glucocorticoids are also reported to inhibit PG production and, in large doses, to suppress inflammation accompanying various clinical conditions, we investigated the effects of hydrocortisone (HC), and methylprednisolone (MP), administered in large doses (100 mg/m2/d of MP or 2.5 g/m2/d of HC) on the above three forms of acute inflammation in rabbits. The effect of indomethacin treatment was studied in parallel for comparison. Blood flow, protein exudation, and leukocyte infiltration were quantitated simultaneously with 86Rb Cl, 125I-labelled rabbit albumin and 51Cr labelled blood leukocytes. Systemic indomethacin therapy decreased the blood flow and permeability, while local indomethacin (2.5 micrograms) significantly inhibited leukocyte infiltration into the lesions. In contrast, HC and MP caused only a mild decrease in blood flow, without altering protein exudation or leukocyte influx. However, HC and MP did inhibit protein exudation induced by bradykinin or histamine injection. These results indicate that, at least in rabbits, HC and MP, in contrast to indomethacin, have very weak anti-inflammatory actions on three complement- and neutrophil-mediated inflammatory responses, i.e., E. coli, ZAP (C5ades-arg) and reversed Arthus reactions.

Mummification of the infarcted myocardium by high dose corticosteroids

There is evidence that glucocorticoids reduce infarct size but their use in myocardial infarction remains controversial because of their potential adverse effects on healing of the infarct. To investigate the healing process, rats received either four parenteral doses of 50 mg/kg of methylprednisolone (MP) or saline 5 min, 3,6 and 24 hr after coronary occlusion and their hearts were examined by light and electron microscopy 48 hr and seven days after occlusion. At 48 hr, in five untreated rats, only 12 +/- 7% of injured myocytes showed the persistence of striations and a relatively intact sarcolemma despite loss of nuclei and hence appeared "mummified" whereas in six MP-treated rats 72 +/- 8% of myocytes exhibited this appearance (P less than 0.001). In treated rats there were fewer phagocytes than in controls. At seven days, in seven MP-rats, mummified cells were still more prominent than in five untreated rats and there were fewer phagocytes and less collagen. In conclusion, high dose of MP delays the inflammatory process and retards the disintegration of necrotic myocytes, resulting in impaired healing.

Methylprednisolone pulse therapy in the treatment of polyarteritis nodosa

Two cases of lung granulomata associated with "crescentic" glomerulonephritis both in a clinical setting of polyarteritis nodosa were treated with high doses of intravenous methylprednisolone ("pulse therapy") in single injections of 30 mg/kg body-weight. In the first case rapidly progressive glomerulonephritis with 100% crescents was arrested and followed by improvement of renal function from a creatinine clearance of 5 ml/min to 30 ml/min; in the second case multiple lung granulomata of 8 months' standing, unresponsive to oral steroids, disappeared 8 days after treatment with high dosage intravenous methylprednisolone. The use of "pulse therapy" with methylprednisolone is advocated, not only in such cases where arteritis is known or suspected, but also in radidly progressive glomerulonephritis associated with crescents.

Protective effect of methylprednisolone on ischaemic myocardium assessed by ventricular function

Intracardiac surgical procedures are best carried out when the heart is still and bloodless. This condition, however, produces myocardial cellular damage with loss of contractility and compliance unless some protection can be provided. Myocardial contractility and compliance is best studied by isovolumic ventricular function tests, which were used to evaluate the protective effect of methylprednisolone on the isolated cross-perfused canine heart made ischaemic for 2 hours. Control experiments included 2 hours of ischaemia without methylprednisolone, and 2 hours of continuous normothermic cross-perfusion. The methylprednisolone-treated hearts had probably significantly better ventricular function after 2 hours of ischaemia than did hearts without the methylprednisolone, while the cross-perfused hearts were best overall. This work suggests that methylprednisolone may have a protective effect on the ischaemic myocardium of the intact canine heart.

Neutrophil preservation: the effect of short-term storage on in vivo kinetics

A rabbit model was developed to study the in vivo viability of neutrophils stored in vitro for up to 72 h. Acid-citrate-dextrose anticoagulated whole blood was obtained from rabbits previously injected with tritiated thymidine ([3H]thymidine), stored under varying conditions, and then injected into recipient rabbits. Neutrophil viability and function were assessed by measuring the ability of the tagged neutrophils to circulate and to migrate into subcutaneous polyvinyl sponges. Unstored neutrophils disappeared exponentially from the circulation with a t1/2 of 3.2 h and gave a zero time recovery of 30.5%. Storage of cells at either room temperature or 4 degrees C for 24 h or longer resulted in temporary sequestration of cells from active circulation. With cells stored for up to 72 h at 4 degrees C, recovery returned to normal values after 1-2 h. Room temperature stored cells, in contrast, showed evidence of irreversible damage at 48-h storage with low recovery for the entire time span studied. With unstored blood, 8.1+/-0.9% of the injected neutrophil label was present in the subcutaneous sponges. The accumulated label progressively decreased as cell storage time increased reaching at 72 h 5.1+/-0.6 and 2.6+/-0.3% for 4 degrees C and room temperature-stored cells, respectively. The results of this study indicate that 4 degrees C storage of rabbit neutrophils is superior to storage at room temperature. The data suggest that it may be feasible to store neutrophils at least a few days without loss of in vivo functions.

Rat polyvinyl sponge model for the study of infections: host factors and microbial proliferation

Female rats were treated with several administration regimens of methylprednisolone, cobra venom anti-complementary factor, and cyclophosphamide in conjunction with polyvinyl sponge implantations. The effect of these drugs on host factors active against bacteria was evaluated with Staphylococcus aureus ATCC 25933, Escherichia coli K-12, and Pseudomonas aeruginosa CDC 7725. One of two implants in each animal was infected with 10(8) of one of the three bacteria, and bacterial and granulocyte content was determined in the infected and control sponges after 48 h. The single large dose of methylprednisolone decreased staphylococcal and E. coli clearance while promoting dissemination of P. aeruginosa. A low chronic dose of the steroid inhibited E. coli chemotaxis only. A higher dose of the steroid administered chronically interfered markedly with S. aureus and E. coli curtailment by the host while leading to enhanced dissemination of P. aeruginosa, accompanied by a precipitous decline in granulocytes. Results with cobra factor resembled the higher chronic dose of steroid enhancing, especially the dissemination of the pseudomonad and its anti-granulocytic propensity. Cyclophosphamide depression of granulocytes revealed the rat's ability to curtail the proliferation of particular S. aureus and E.coli strains even in the absence of leukocytes. This treatment resulted in the rapid spread of P. aeruginosa, leading to the death of some experimental animals. These experiments underline the versatility of this animal model in the study of host and microbial factors influential in infectious disease.

Rat polyvinyl sponge model for the study of infections: initial investigations

Polyvinyl sponges were implanted subcutaneously on both sides of young female rats. One sponge was infected with 10(8) of either Escherichia coli K-12 F-, Staphylococcus aureus ATCC 25923, or Pseudomonas aeruginosa CDC 7725. P. aeruginosa remained at the inoculum level and S. aureus declined by 1 log, whereas E. coli was reduced 1,000-fold. Only P. aeruginosa was recovered from the blood in 36% of the animals in 24 h and in 20% of the rats in 48 h. The nutrient potential of rat inflammatory fluid was compared to nutrient broth by growth of each bacterium in untreated and heat-inactivated sponge fluids and Trypticase soy broth.

Fibroblast DNA synthesis activation in sponge induced granulation tissue. The effect of antineutrophil serum and cyclophosphamide

DNA synthesis in rat and rabbit polyvinyl sponge induced granulation tissue has been studied using thymidine (methyl-3H). Synthesis was determined by measurement of thymidine incorporation into cold trichloroacetic acid insoluble material and by autoradiography. Granulation tissue was removed and immediately incubated in vitro in the presence of thymidine (methyl-3H) for three hours. The label was incorporated into the nuclei of fibroblasts and, to a lesser extent, of endothelial cells. The labeled material was 93% lysable by DNase and its synthesis was inhibited by hydroxyurea and bleomycin. In this system synthesis was linear for two hours and then ceased. A marked increase in DNA synthesis occurred in tissue harvested at 44 hours after sponge implantation. This rise was confirmed by autoradiographic studies which showed an increase in nuclear labeling at two days after implantation. Neutropenia produced by injections of antineutrophil serum or cyclophosphamide failed to inhibit activation of DNA synthesis in fibroblasts or endothelial cells. Amonocytosis also had no effect on this process. Rates of thymidine incorporation into DNA and thymidine phosphates in vivo were similar to those found during in vitro incubations of granulation tissue.